These studies present the results of use of mixture of sunflower (Helianthus annuus L.), climbing bean (Phaseolus vulgaris L.) and marigold (Tagetes L.) which was sown on the margins of organic potato fields. The necessary agrotechnical measures were performed. The plants on the margins were used as the mechanical barrier for spores of. P. infestans. Also beneficial insects occurring on margins were observed. As a control area it was used the field without the strips with mix of plants, but with the same agricultural practices. During growing season the healthiness of plants was monitored. Symptoms of late blight were noted. Beneficial insect living in the strips according to adjacent crops were noted, most insects were observed in the strips from the field of rape.